Current evidence shows that Risk for Sudden Infant Death Syndrome (SIDS) is associated with a subtle neurological defect producing hypoventilation during sleep, chronic hypoxia, and axial hypotonia during waking. Defects of the medial reticular formation of the brain stem are hypothesized to account for risk for SIDS. The proposed studies will assess a series of hypotheses about the role of medial brain stem RF neurons in regulation of ventilation in normal and hypoxic kittens and cats in both neutral and cool temperatures. Studies will focus particularly on conditions and sleep states associated with either ventilatory compensation or depression in response to hypoxia. We will monitor continuously parameters of sleep physiology, tidal volume, diaphragmatic EEG activity, and relates parameters of breathing, and, in some studies, medial RF unit activity in unrestrained kittens and cats. By using vestibular stimulation (rocking bed) we will augment medial RF unit activity in order to test the hypothesized reticulo-respiratory facilitation. We will also employ a relatively cell-selective lesion technique in the medial RF to produce a subtle defect model of SIDS, testing for altered sleep-related ventilatory control. Finally, we determine optimal parameters of rocking-bed facilitation of breathing during SWS and REMS as well as assess the long-term stability of this potential clinically-useful approach to sleep-related hypoventilation.